A refrigerator is a home appliance to allow a user to keep food fresh. Conventional refrigerators have a thermally insulated structure prepared by filling a urethane foaming liquid in an empty space of an assembled structure of an outer case and an inner case, by filling a urethane foaming liquid in an empty space of an assembled structure of an outer case having a vacuum insulation panel (VIP) attached to an inner surface thereof and an inner case, or by mixing an aerogel with the urethan foaming liquid.
Decrease in power consumption is limited by using insulation walls having a structure including only urethan foam unless thickness of an insulation material is increased. As the thickness of the insulation material increases, a volume of an inner space of a refrigerator decreases and an amount of urethane foaming liquid increases, thereby increasing manufacturing costs of the refrigerator.
If the vacuum insulation panel (VIP) is applied to decrease power consumption, the vacuum state of the VIP may be destroyed resulting in difficulty in maintaining power consumption, a space for urethane form is not sufficient due to the introduction of the VIP, and a cabinet of the refrigerator may have a non-uniform surface.
Also, the insulation wall formed by mixing a urethan foaming liquid with an aerogel may not have sufficient heat-insulating performance since independent foam generated while curing urethane may be destroyed by the aerogel.